Spacers (also known as, for example, chambers, dispersion chambers, valved chambers etc.) for use with MDI's are known. The benefits of using a spacer with an MDI to deliver medicaments may include assisting a patient to self-administer MDI medicaments. For example, a spacer may improve the delivery of the inhaled drugs to the patient's bronchial tubes and/or lungs by breaking up, slowing down and/or dispersing the discharged medication to enhance mist formation and reduce oropharyngeal deposition.
Spacers have traditionally been designed for re-use. They are therefore typically made from rigid polymeric materials or the like and require a user to ensure they are kept in good working condition which involves regular cleaning to avoid the accumulation of deposited medicaments and bacterial contamination. Some examples of reusable spacers are described in U.S. Pat. No. 4,174,712 (Moren et. al.), U.S. Pat. No. 4,470,412 (Nowacki et. al.), U.S. Pat. No. 5,012,803 (Foley et. al.), U.S. Pat. No. 5,385,140 (Smith), U.S. Pat. No. 5,427,089 (Kraemer) and U.S. Pat. No. 5,816,240 (Komesaroff).
While spacers are generally cylindrical in shape, other shapes have been described. For example, U.S. Pat. No. 7,107,987 (Sundaram et. al.) describes a spacer having a first conical body joined to a second conical body. When in use, the spacer is described as limiting deposition of the medicament by channelling the spray down its centreline which reduces contact between medication particles and the walls of the spacer. The spacer design is described as taking advantage of the high-pressure recirculation zones that tend to force the medication spray away from the walls of the spacer into a preferred, central spray pattern so that a high percentage of the medication is delivered deep into the lung regions of a patient. In one embodiment the spacer comprises a unidirectional valve provided proximate to the mouthpiece. In another embodiment the spacer comprises at least one conical body that is collapsible so that the spacer occupies less storage space when not in use.
Another type of spacer design is described in U.S. Pat. No. 7,201,164 (Grychowski et. al.). The spacer comprises a holding chamber which tapers to a narrow orifice from a medicament upstream end to a downstream end. Preferred embodiments comprise inhalation and exhalation valves. The narrow orifice alone or in conjunction with the tapered channel is described as maximising the emitted dose and respirable fraction of the aerosol, more specifically, increasing the velocity and the number of respirable particles and concentrating them along the axis or centreline of the channel. The spacer is said to be particularly suited to users (such as children or the elderly) with low tidal volumes.
U.S. Pat. No. 6,345,617 (Engelbreth et. al.) describes an aerosol medication delivery apparatus which comprises a canister-holding portion and a chamber housing. The chamber housing includes a containment baffle that partially blocks the output (i.e. mouthpiece) end. The containment baffle is described as having a concave surface facing the input end and functions to reduce the velocity or flow rate or both of the aerosol medication particles which are delivered from the pressurised MDI along the longitudinal axis (i.e. axis of symmetry) of the chamber housing. The aerosol medication particles that have a flow path away from the axis of symmetry tend to have a velocity that is lower than that of the particles near to the axis of symmetry. Further, it is described that upon discharge, the on-axis aerosol medication particles which are generally non-respirable and have a higher inertia than the respirable particles, collide with the interior centre portion of the containment baffle resulting in a reduction in the number of larger (non-respirable) aerosol medication particles into smaller respirable particles. In one embodiment the containment baffle is described as having four relatively large openings formed around the periphery of a solid dish-shaped central portion to provide a surface area that serves to prevent aerosol particles having a high velocity from passing to the patient.
Disposable spacers are known. For example, U.S. Pat. No. 4,953,545 (McCarty) describes a plastic disposable chamber which tapers, much like a take-away coffee cup, outwardly from the MDI input end towards the mouthpiece end.
Collapsible and/or expandable disposable spacers are also known. For example, U.S. Pat. No. 6,202,643 (Sladek) (see also related U.S. Pat. No. 6,550,473 (Sladek) and U.S. Pat. No. 6,679,252 (Sladek)) describes a collapsible, disposable valved chamber which may be constructed from a single punched sheet of suitable material such as paperboard, plastic, spun non-woven polymer such as TYVEK by DuPont or the like. A key feature of the invention is the one-way inhalation valve is described as being disposed between the mouthpiece opening and a first volume of the chamber to allow a one-way flow of gas from the first volume to the mouthpiece opening. The one-way inhalation valve is further described as including an inhalation flap (or membrane) and valve seat. Exhalation by a patient through the mouthpiece opening presses the inhalation flap against the valve seat to prevent the flow of exhaled gas from the mouthpiece opening back into the first volume, the exhaled gas flowing through an opening in the mouthpiece section between the one-way inhalation valve and the mouthpiece opening. Inhalation by a patient through the mouthpiece opening causes a portion of the inhalation flap to move away from the valve seat to provide a path for the flow of gas from the first volume into the mouthpiece section. In use, the patents describe that the relative vacuum created by the patient's inhaling causes the inhalation flap to pivot or swing away from the opening in the inhalation valve panel. This is to enable a substantial portion of the ejected plume of medication to pass through the inhalation valve opening and the mouthpiece end opening into the mouth of the patient. When the patient exhales before repeating the above procedure the inhalation flap is forced, by the increased pressure caused by the patient exhaling, against the peripheral portion of the inhalation panel around the inhalation opening. The exhaled air then flows through an exhalation opening as it pushes an exhale flap outward so that the exhaled air escapes to the outside atmosphere.
Related U.S. Pat. No. 6,679,252 (Sladek) describes a further embodiment of the construction and operation of the expandable/collapsible valved chamber from a single sheet (see for example FIGS. 19A-F). Notably described is the formation of a good seal to prevent both the inhaled and exhaled air from bypassing the inhalation valved chamber which is said to substantially increase the efficiency of the valved chamber. Referring to FIG. 19E, when the valved chamber is fully “popped-up” for use by a patient, the panel comprising the inhalation valve is in a nearly vertical position thereby providing a nearly vertical wall that separates the first volume between the inhalation valve assembly and the MDI boot adapter panel and a second volume between the inhalation valve assembly and the inhalation/exhalation openings.
A common feature of known spacers, including those described herein, is the tendency to comprise a valve or diaphragm arrangement to control the flow of air through the spacer as the patient inhales and/or exhales the medicament. The valves may typically be made from polymeric materials and when employed for reusable spacers, require regular cleaning to avoid the accumulation of deposited medicaments and bacterial contamination. In the case of, for example, the collapsible/expandable and disposable spacers described in U.S. Pat. Nos. 6,202,643, 6,550,473 and 6,679,252 (above), the inhalation valve assembly comprises a flexible inhalation flap (or membrane), specifically a transparent plastic film adhesively attached along one edge to the inner surface of the inhalation valve assembly panel to cover the inhalation hole. Alternatively the inhalation valve flap may be hingeably connected to the inhalation valve assembly panel by a plurality of short, spaced hinge points.
The present invention provides an expandable/collapsible and in a preferred embodiment, disposable spacer for use with a MDI. The spacer is believed to possess one or more advantages or improvements over known expandable/collapsible and disposable spacers.